1. Field of the Invention
The present invention relates to a clamping apparatus for fixing a workpiece or other object of clamping to a bed under pressure, and more particularly, to a clamping apparatus capable of clamping any objects of clamping with different heights and permitting easy setting and removal of the object.
2. Description of the Related Art
In conventional clamping apparatuses which fix a workpiece to a bed of a machine tool by utilizing the clamping force of screws, a clamp piece is stretched over the workpiece and a base block placed on the bed, and a clamp bolt is located penetrating the intermediate portion of the clamp piece. A tip screw portion of the clamp bolt is connected to a T-nut or the like, which is fitted in a T-groove of the bed, whereby the workpiece is fixed to the bed.
In order to apply one such clamping apparatus to various workpieces with different heights, it is necessary to provide base blocks of different sizes corresponding to the heights of the workpieces. Without the use of the various base blocks for the individual cases, the clamp piece tilts, so that a horizontal force acts thereon as a pressure screw is tightened. Accordingly, the clamp piece may slip on the workpiece, or otherwise, the workpiece may slip on the bed. Thus, the workpiece cannot be stably fixed under pressure. If the pressure screw is loosened for the replacement of the workpiece, moreover, the clamp piece can be easily disengaged from the base block. The setting of a new workpiece, therefore, requires repetition of the aforementioned operation.
Meanwhile, some of these clamping apparatuses are improved in the applicability to workpieces with various heights and in the efficiency of replacement of workpieces. Among these conventional apparatuses, there are ones which have a hydraulic-cylinder structure such that a clamp piece is fixed to the tip end of a piston rod, and a male screw to mate with a female screw on the bed is formed on the outer peripheral surface of a cylinder tube. These clamping apparatuses must, however, be provided with means for threadedly fitting the cylinder tube into the female screw of the bed and means for adjusting the depth of threaded engagement in accordance with the height of the workpiece. These apparatuses can be applied only to those beds which have a female screw with an inside diameter large enough to mate with the male screw on the outer peripheral surface of the cylinder tube.
The clamping apparatuses of the conventional construction utilize the clamping force of the clamp bolt which penetrates the clamp piece stretched over the workpiece and the base block. These apparatuses are poor in the applicability to workpieces with various heights and in the efficiency of replacement of workpieces. In the clamping apparatuses of the hydraulic-cylinder construction, with the male screw on the outer peripheral surface of the cylinder tube, moreover, the male screw serves both as means for connecting the apparatus to the bed and as means for adjusting the level of the clamp piece. Accordingly, the clamping apparatuses of this type can be used only with those beds which have a female screw with an inside diameter large enough to mate with the aforesaid male screw.